"Any guesses what it's used for?"
"Well it would definitely affect brain chemistry, so it could be used as some kind of a drug or stimulant I suppose."
Terrazine gas is a potent psionic reagent. It is sought by protoss, zerg and terrans alike. The protoss consider it "the Breath of Creation" (literally translates as such via Khalani). The Tal'darim believe that terrazine is a gift from the xel'naga to allow communication with them.
The properties of terrazine appear to be foreign to the material universe—it has been speculated that terrazine's origins lie within the Void, as on Slayn, it was found in the presence (or emitted) large amounts of Void energy. The presence of terrazine in large amounts can sustain Void shades, albeit not at full strength. The Tal'darim used terrazine to become closer to Amon and to "peer beyond the veil."
Terrazine is similar to vespene gas, and contains additional organic substances, though is not as flammable. Without special preparation and containers, samples don't last long. Visually, terrazine has appeared to be purple and misty green.
Terrazine has a coppery, blood-like smell.
Biological and PsychologicalEdit
Its effects are unpredictable, though it possesses mind-altering qualities and can enhance the psionic power of ghosts and other psychics, increasing their power by 1 or more points on the Psi Index scale, though the effects would probably not be noticable on an individual possessing an average PI. Gabriel Tosh believed this could increase a ghost's powers to near those of the protoss. Terrazine also rejuvenates a terran's brain cells, allowing them to overcome memory wipes and other such treatments. At least some spectres can also more easily resist mind-reading and can avoid picking up unwanted thoughts.
Terrazine's side effects include hallucinations and violent outbursts. The exact effects vary somewhat from one individual to another. Many spectres became eccentric, collecting devices such as dolls in an effort to enhance their powers.
Nova Terra claimed that terrazine drove the users insane, and the instability resulted in the shutdown of Project Shadowblade. Tosh and an independent researcher, Dr. Ariel Hanson, said that Terra had exaggerated its effects.
Terrazine has a half-life of several hours, but it builds up in the system over time and with repeated use. It is addictive, causing withdrawal symptoms after several hours. Stabilized by a little jorium, terrazine is inhaled by spectres like a drug. If the spectre keeps to a strict schedule, the side effects are minimized.
Terrazine is a substance with a composition foreign to our universe, and was likely brought from the void by Amon. It has been used by the Tal'darim for millennia, as a holy object they believed brought them closer to the xel'naga. They spread it across a myriad of planets, converting them into shrine worlds. This process has proven catastrophic to the native life, as shown by the destruction of the jungles of Slayn.
The Second Great WarEdit
During the Second Great War, Gabriel Tosh commissioned Raynor's Raiders to steal terrazine from protoss altars on Bel'Shir. The altars were guarded by the Tal'darim, who regarded the gas as a sacred gift from the xel'naga, and refused to give the terrans any. The Raiders took what they needed by force.
The End WarEdit
During the End War, the Tal'darim Alarak sought out Hierarch Artanis for aid in challenging Highlord Ma'lash, so he might claim his title and cease hostilities with the Daelaam. Upon arriving at the Tal'drim homeworld of Slayn, Alarak tasked the Daelaam to target Ma'lash's four lieutenants on the surface. During the battle, terrazine would rise from the underground, in which Amon's forces would emerge and attack until the mist subsided. After successfully killing Ma'lash's lieutenants, Alarak breathed in the terrazine and was pleased to feel Amon's fury at his defiance.
This article or section contains information about StarCraft: Ghost, which has been declared non-canon. Elements may be taken as 'flavor lore' however.
Mar Sara featured a Dominion-operated "Vespene" Refinery BF 1138, a terrazine refinery on Mar Sara, disguised as a vespene refinery, which was infested by zerg and had to be rescued by Nova (a ghost) and other Dominion forces.